


Cursed Experiment

by anothermiya



Category: Shingeki no Kyojin | Attack on Titan
Genre: Age Regression/De-Aging, Babysitter Levi Ackerman, Erwin Smith Is A Little Shit, Everyone loves kid Erwin, Fluff, Hange Zoë's Experiments, Kid Fic, Levi is basically a parent, M/M, Sickfic, Tooth-Rotting Fluff, kid erwin
Language: English
Status: In-Progress
Published: 2021-03-11
Updated: 2021-03-11
Packaged: 2021-03-18 02:34:40
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,368
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29976072
Author URL: https://archiveofourown.org/users/anothermiya/pseuds/anothermiya
Summary: It started when Erwin got his seasonal sickness and Levi gave him the wrong medicine which turned Erwin into a kid. Little did he know, kid Erwin could make him see the light.Alternate summary :Basically Levi needs to babysit Erwin as long as Erwin is in his kid form.
Relationships: Levi Ackerman/Erwin Smith
Comments: 8
Kudos: 26





	Cursed Experiment

Per usual, Erwin is sitting on his desk and doing papers until he feels his head pounding like crazy. It's always like this once in a while. He should get used to it, but he could never. A knock on his door brings his consciousness back again. He looked up and saw Levi with another paper on his hand. He smiled and let Levi sit on the chair across him. They both keep the voice low to their liking and do their own job. Well Levi just accompanied him while peeking into Erwin’s paper. It’s nice to see those handwriting. So neat and satisfying.

After a while, Levi noticed that Erwin isn’t in his best condition to work. He sighed and put the paper down. "Season sickness?" Levi finally asked. He put his hand on Erwin’s forehead and was surprised because his temperature is pretty high.

"Is it winter already?" 

"Yeah. Still early though for you. Go back to our chamber or I’ll drag your asses myself. I'll get the medicine for you.”

"That's a nice way to talk to someone who’s currently sick."

"Tch. You better be at your bed when I get back." 

Erwin waited until the door closed before continuing his paper. He knew that Levi knew he won't go back to their shared chamber. And he knew that Levi won’t mad at him, because he’s sick. Everyone will spare him whenever he gets sick and he takes advantage of it. At the other side, Levi stormed through the hallway and barged into Hange's nest, laboratorium. He observes the laboratorium first and finds so many samples of titan’s fresh flesh and blood. He doesn’t know what Hange trying to make, but decided to not putting that on mind. 

"Where's Erwin's usual medicine."

"On the second shelf. You know which one it is." 

Levi walked towards the shelf and took one of the flasks on there and wondered if it’s the right flask. After confirming it with Hange, he brought it to Erwin who he knew still in his commander room. Erwin looked at him with a faint smile on his face while signing another paper. Levi sighed in defeat. See, he didn't drag him out like he said before, instead he just took his usual chair and gave Erwin the flask with a glass of water.

Erwin drank the liquid in one gulp and drank mineral water to neutralize his mouth from the bitter taste. Usually, the medicine will take effect after a while, but it's different. His head started pounding harder and his whole body trembled. Levi jumped out of his chair and held Erwin still. "Erwin! Did I give you wrong medicine!?" He panicked as hell. He snatched the glass away before Erwin dropped it and made a mess. Erwin writhing in pain and let Levi support his body. 

"LEVI! WHERE'S THE FLA—"

"Hange! What the hell is in that thing?"

Before Hange could answer his question. Erwin's hand already shrinking, Levi looked at him cautiously without letting him go from his grab. "It's a de-aging serum. Honestly it's an anti-aging serum, but there's some miscalculation and make it as a de-aging serum. I'm so sorry!" Hange said. 

"But you said, it’s the usual medicine!?”

“It has the same flask. I’m so sorry!”

“Then why did you put it on the same shelf or, why the fuck did you make it in the first place!? Where's the cure?"

"Still working on it! Gimme at least a week. Please!"

"What should I do with him?"

"I don't know. I'll leave him to you, I'm counting on you, Levi!" They screamed before leaving Levi with the small Erwin. Oh he’s fucked up.

Levi gritted his teeth and looked at Erwin who's now shorter than him. He looks cute. With his round blue eyes which are so fascinating. Okay, stop. Levi needs to do something with him. Erwin leaned over and clung onto his arm with his small trembled hands. 

"Can you move?" Erwin shook his head softly and bit his lips. He reached Levi's fore finger and held it tight. Levi touched Erwin's forehead and it's burning hot. He immediately carried Erwin in his arms and brought him to their shared room. He lay him on the bed and put off his gear to let him breath. He gave him wet cloth and put a thick blanket over him. He caressed his blond hair and let him rest for a little bit. 

"Erwin. On scale one to ten, how much is it hurt?" Levi asked after Erwin seems a little bit calmed down.

"Eight." 

"Great. At least not ten."

"May I know who you are, Sir?" 

"Let's talk about it later. Stay on your bed. Don't go anywhere, I'll go get something for you."

"Mkay…" 

Levi never run so fast before, but today is so fucking different. He arrived at laboratorium and found Moblit cried his ass off because of Hange. "Have any fever medicine?" Levi asked while panting from the door. "It's better to give him painkillers for now." Moblit answered while wiping his tears. He got up and looked for the pills. He’s traumatized to give him anything based on liquid and it’s his way to avoid other weird things happening. 

After a few minutes scrambling through his cabinet. He gave Levi a pack of pills. "Moblit, could you buy some clothes for Erwin?" and Moblit nodded to answer him and then sniffed out loud to release his stress. Levi handed him his money and took the painkillers with him. "Buy at least four pairs of clothes. Got it? And good luck with that shitty four-eyes." Levi said before going back to his chamber. 

When he opened the door, he saw Erwin clutching to the bed and it hurt him so much. He sat beside him and gave him a soft massage on his temples. "Sir, Is it winter already?" the little Erwin asked. He’s so polite. Mr. Smith surely taught him very well. Levi nodded and let out a faint smile. "Yeah. Got season sickness?" asked him back.

"I think so. I'm sorry for bothering you."

"No, you don't. Can you get up for seconds?" 

The little boy nodded and got up from the bed. He waited for Levi who still grilled the pills into powder. It must be hard for him to eat pills. Levi put the powder in a spoon and gave it water. “It’s really bitter so you better drink the water immediately after it, okay?” Erwin nodded and opened his mouth. Levi feeds him the medicine and makes sure he won’t throw the medicine up. Erwin squeezed Levi’s arm and his eyes started to get teary. After swallowing the medicine, Erwin drank almost the whole bottle and pouted. 

“I hate medicine.” He said. And Levi just scoffed, he knew.

“Go get some sleep.” Levi said while putting the bottle and the spoon away, but Erwin grabbed his hand and looked at him with his teary eyes. Oh the habit of this man, or kid? Now, he needs to stay with him until his condition is better, yeah he knows it. It’s still Erwin after all.

"I… I'm sorry. My father used to hold me when I was sick." He stuttered. 

"I know."

"You know?" Levi answered his question with a single nod. He sat on the edge of the bed and let small Erwin rested his head on his lap. It's his habit. Levi knows it really well. He didn't spend nine years getting to know him for nothing and it's good that this happened in winter, because the Survey Corps doesn't have that many agenda in winter. 

"My name is Erwin Smith. Seven years old. What about you, Sir?"

"Levi. I'm much older than you. So you have to listen to me. Other than me is prohibited"

"Okay and nice to meet you Mr. Levi."

"Just Levi. Fuck formalities."

"My dad said we shouldn't use bad language, Levi. Ah! My dad! I need to go back to my house." 

"No. There's something happening to you and you need to stay here until everything is resolved. Got it?"

"Is my father in danger, Sir? I mean, Levi?"

"No he's fine. He got some business to attend, so you just need to stay here, okay?"

"Okay."

"Okay now, on a scale one to ten how hurt you are now?" Levi asked again. 

"Seven?"

“Then, you should sleep to make it zero.” Levi plays his fingers with the blond hair and continues giving the small one a soft massage on the head. He looks so soft. His cheeks look like cotton. It's so different with the old Erwin. He still remembers how his jaw is so sharp and defined so finely. He misses old Erwin already. 

And now comes the real problem. How is he supposed to take care of this kid? This small Erwin. He knows nothing about children, since he didn't grow up properly. He zoned out for solid minutes and snapped back after Erwin hugged his waist. This little creature buried his face on his belly and it successfully made Levi laugh. Habit never dies huh, guess it’s right all along.

Levi touched the forehead of the small Erwin and the burn is slowly going down. He kissed his forehead briefly and joined him to the dreamland. 

Hours have passed. Small Erwin awoke from his sleep because the sound of knocking on the door reached his ears. He can feel that his pain was fully gone. He looked up and saw Levi still sleeping peacefully. He smiled at the sleeping Levi. Another knock can be heard and it reminds him that he needs to open the door. He got out of bed after covering his naked body with the blanket and when he opened the door, he found a man with a paper bag in his hand. 

"Good evening. Is Levi there?" he asked with a swollen eyes on his face. Is he okay? Erwin thought.

"He is sleeping. May I help you, Sir?"

"Oh that's very nice of you, commander. Then, can I give it to you." He handed him the paper bad to Erwin and gave him a half-assed smile. He’s in pain, Erwin thought again. 

"Who’s commander? And what is this?"

"Oh my bad, just don't mind me and it’s your new clothes. I hope you liked it.”

"Erwin. Who's that?" Levi asked 

"It's me, I brought the clothes you asked."

"Ah thank you Moblit and please keep it down for a while, will you?" 

"You're welcome and sorry about everything. We will make the antidote as fast as possible. Then good evening, captain."

Moblit smiled at Erwin before saluting him. After he left, Erwin closed the door and gave the bag to Levi. He snuggles onto Levi and sits on his lap, so he can take a look at what's in the bag with him. Levi rested his chin on top of Erwin's head and hugged him briefly, but he immediately frowned and pushed him away. "You should take a bath. You smell like sewage water." Levi said while covering his nose to prevent the smells damaging his respiration system.

"You're so mean, Levi."

"Better get used to it. Come on. You're sweating a lot whenever you are sick and it's gross." 

"You speak like you know me that much. I'm impressed. Are you my father's friend?" 

"Just acquaintance." 

He grabbed Erwin's waist and carried him like a potato sack on his shoulder. His small body really gave him a lot of advantages and with his mental state right now, maybe he can win against him. Or not? This is Erwin we're talking about. 

Levi put him down in the bathroom and forced him to take a bath. "If you finished. Go back to the chamber straight away and wait for me. I’ll bring you tea and something to eat." Erwin nodded and closed the door before him. He really takes a bath, carefully because it's cold and he wants his body to be clean, like Levi said. He is an obedient kid after all. 

After almost ten minutes in the bathroom, he got out with chattering teeth and a shivering body. He called out Levi, but no answer. He dried his body using the towel and wore his new clothes. It smells so fresh, unlike newly brought, but who cares. He exited the bathroom and walked toward his room. But a big hand stopped him on track and scared him a little bit.

"Hey! Who are you!" 

"I… I'm… E-" it's really hard to talk with chattering teeth. 

The two men drag him downstairs and bring him to another building, Erwin just let them, because he doesn't like to fight moreover with someone who's definitely able to beat him to pulp. And they ended up in the dining room, where Levi is. He looked at Levi with his apologizing look, so he wouldn’t get mad at him.

"Captain! He's an intruder and I caught him on the third floor in the building one. Wandering alone." the man reported. Erwin pushed forward and many soldiers gasped. They're pretty much shocked when looking at Erwin, small Erwin. "I told you to go back to the bedroom? Haven't I?" Levi asked with an irritated look on his face. It's scary, Erwin thinks. 

"S-sorry. They found me and dragged me before I got into the room." 

"Come here." Erwin ran towards him and hugged Levi’s legs. Levi put off his coat and put it on Erwin and gave his tea to make Erwin feel warmer. 

"Since he's already here, I got an important announcement. So this is Erwin, the small one. There's something that happened which I can't tell you and you better keep it secret. Don't let the higher up hear about this. Got it!?"

"Understand captain!" 

Levi ruffled Erwin’s blond hair and made him sit next to him, just like how the kid wanted. Across them, it's another of his comrades. "Levi… I was wondering about where I am. Do you mind telling me?" Erwin asked. He put the glass down and waited for an answer.

"Unfortunately, you're in Survey Corps headquarters."

"Oh! So you're the one who goes outside the wall to do some expedition and kills the titan?"

"Yeah."

"So how's outside the wall?"

"Not bad..."

"I always told my father that I wanted to go outside the wall, but he didn’t let me. I asked why and he said I’ll just waste my life to get eaten by a titan. So Levi, do you think I would get eaten by the titan once I stepped outside?” Erwin asked with all of his innocence. 

“No!” Levi spontaneously raised his voice and snapped the spoon on his hand. It scares the hell out of Erwin. It's bad, the idea of Erwin getting eaten scares him so much. Never once he imagine Erwin die, let alone getting eaten by a fucking titan. 

"Captain, calm down please. He's a kid." One of his comrades said. It brings him back to reality. He looked at the pale Erwin and sighed when can feel Erwin’s fear toward him. "I'm not sorry for scaring you, but really you shouldn’t talk about titan in the dining hall. understand?” Erwin nodded and continued his meal. 

The problem is, Erwin starts pouting and already holds his tears back until his body trembles. "Erwin..." Levi called him. The boy put his utensils down and faced Levi with his teary eyes. It’s not fair. How can Levi get mad at this cute thing.

"Levi. I'll try not to make you angry again by not talking about the cursed object and I'm so sorry for my rudeness." Levi chuckled by his word choice and facing the small Erwin.

"You're not mad at me?" Erwin asked while tilting his head.

"Just a moment ago, but now it's fine and after this, let's make some rules. How's that sound?"

"Oh! I like rules. Can I make rules too?"

"Hmm."

"Will you follow the rules?"

"If it's good, then I might."

"Cool!" Levi nodded at him while giving him a pat on his head. 

The dining room gets quieter and Erwin is still finishing his tea. Levi patiently waited for him while reading a newspaper on the desk. 

"Hey Erwin, want to play with me later?" Levi glared at him and gave him a warning. Yes it’s child Erwin, but he is still their commander and no one should disrespect him like that. What’s with the casualty? He’s not friends. In this survey corps, they’re still commander and subordinate. 

"No. Levi and I will make some rules, so I can't go with you." 

"Remember who he is. So don't." Levi said in a low tone to show his irritation. 

"Levi it's fine. They just want to play with me anyway." Ah right! This Erwin doesn't know a thing about anything here, including his old self. 

"If you say so." 

Suddenly Erwin gets off from the chair, "Let's go!" Levi takes their plates to the sink and lets Erwin hold his left hand while walking next to each other. He looked so excited. And Levi couldn't hide his smile anymore. Even though big Erwin has his own cuteness, this small Erwin really could win his heart anytime. 

This small Erwin kept babbling about his father who taught him everything. About the titan, the walls, outside the walls, even about underground which surprised Levi. How can someone this young know so many things already. 

"Oh Levi good that I met you here. I'm still working with the antidote, don't worry."

"I know. Anyway, will his memory get affected because of this?"

"Moblit and I have been thinking about that too and the answer is no, It's because we didn't bring him from the past. I did some research on rabbits, the serum or potion wears off after two months and there's no effect on the rabbit. So don't worry."

"Oh. But the antidote still needs to finish before winter ends, you know that right?"

"I know Levi.”

“Good luck then.” Levi said. Erwin just watched them while sitting on the window while they’re talking. He hopped off and took Levi's hand again after the red haired person left. They went back to their room and Erwin immediately searched for paper and ink to write the rules they will make. Levi just let him do everything since he looks so excited about it. It’s cute to see Erwin getting excited over little things.

On the top of the paper, Erwin wrote 'Levi and Erwin rules!!!' so neatly. It amazes Levi, no wonder why Erwin's handwriting is so satisfying, he got talent. He will not get tired looking at his beautiful handwriting. 

"Write it down. Number one, Erwin must go back to the bedroom before ten." 

"Okay. What about you?" 

"I'm an adult, I can go back whenever I want." 

"But I don't like sleeping alone." Erwin said while pouting. Oh this kid surely knows how to use his weapon against Levi.

"You will not. Okay number two, you can add whatever you want, with my consent."

"Number two. Erwin should NOT make Levi mad again." He said with sparkles in his eyes. 

"Good one. Next, your choice again."

"Three, Levi should let me go outside the bedroom alone or with him." 

"I'm not going to cage you here anyway." Levi said while rolling his eyes.

"Okay so, I'll change it. Number three, Levi should teach me how to use the gear." 

"You're seven, you need to be at least twelve. So, I can't." Levi is strict, everyone knows it.

"Then, you should bring me with you wherever you go, except I don't want to go. I'm not receiving any corrections anymore." Erwin sulked. 

"Okay. Next. Do NOT go outside from the headquarters alone. Tell me if you want to go outside and with whom. Understand?"

"Yes Sir! And next?"

"You choose."

"Five. Levi is mine!"

"Is that a rule?" Levi asked. 

"I don't know. I just want to write it down." 

Levi just smiled. ‘If only you realize Erwin, I've been yours since the day you show me the light.’

**Author's Note:**

> i'm trying to make it fluff, but idk if it's success. sorry if there's any grammar mistake or typos. oh! when Erwin is in kid form, pls don't romanticizing it and sees them as pair of family instead. i'll update once in a week, bcs of school thingies. any critics and comments are welcomed. thank you for reading this fic <3.


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